BitKiller securely shreds files and directories, removing them completely from your hard disk. It can quickly and efficiently overwrite files using anything from random data to the Gutmann method. It also changes filenames to make them harder to find. No setup or installation needed.

For all your audio/video tasks: FFmpeg.
Nothing can beat it and you do not have to pay for it, but a donation is appreciated.

For all your movies and musics watching activities #1: VLC Media Player.
For average users, I have to agree it is definitely the best and most complete multimedia player. Free to use and play, it can still be the preferred choice for enthusiast people. It offers both GUI and Command line interface versions. It can do many things, from watching to streaming. It can record streams as well. Free to use and share, donations are appreciated.

For all your movies and musics watching activities #2: MPlayer.
Command line based multimedia player, it is very powerful and complete. It has great performance and many useful settings. It is current my favorite player. Multi platform support. There are also various GUI versions based on MPlayer if you prefer. Free to use and share, donation is appreciated.

For all your e-mail needs: Mozilla Thunderbird.
Mozilla Thunderbird is a mail client. One of the best alternative to Microsoft Outlook but with much more advantages.

For you music playback and organization: DeadBeef / Audacious/ Clementine.
If you wanted something like Winamp, Windows Media Player of foobar then your hunt is over. Any of the 3 above you give you everything you want and you will be able to organize your music in a very organized way. Did you like them? Donate if you can to help them make it even better.

For all your audio editing needs: Audacity.
You can edit all your audio precisely with Audacity and it also has a wide range of features. It is very good and popular!

For all your CD Ripping tasks: CD paranoia.
Nothing can beat it, EAC is good but its biggest defect is that it is Windows ONLY. Free to use, but a donation is appreciated.

For all your office tasks: Apache OpenOffice or LibreOffice.
Nothing can beat them, MS Office is good but it will cost you a kidney or a liver and let's face it: It has childish interface while OpenOffice and LibreOffice can be used and shared for free and they're almost completely compatible with MS Office documents. While MS Office will limit you to Windows only, with OpenOffice.org or LibreOffice you can create and share your documents on other operating systems as well. Free to use, but a donation is appreciated.

For all your graphics work based on pixels: GIMP.
Let's face it, Adobe Photoshop is only well known and much used because of piracy, Adobe has to thank all the piracy it got till here.
And I doubt the average user will pay thousands of US dollars just to do basic or even more advanced work with it. Unless said user is rich or sold his body organs.
GIMP will do most things, if not all, Photoshop can do and with the big advantage it won't cost you a liver, a kidney or even worse your children to use it. Absolutely free to use, but if you can donate any amount to help the project, even a few cents is appreciated. Let's encourage those great developers!

For all your RAW photography needs: RawTherapee.
I have used already it is great. Support for newer cameras are added quite fast and many bugs are fixed every now and then.

For all your vector graphics work: InkScape.
Forget about Adobe Illustrator or CorelDraw. You can create absolutely everything you can imagine with InkScape. Still doubt!? See for yourself the amazing works PROFESSIONAL and AMATEUR people are creating with this free, open source and cross platform vector graphics program: https://inkscape.org/en/community/gallery/. Warning: You will be amazed!

For all your archiving/backup and file compression purposes: GNU Tar/ GNU Gzip / XZ Utils/ Bzip2.
You won't need anything more. Excellent compression ratio that is freely available in all platforms you can imagine. Obviously, you can decompress your files later with these same tools.

For all your Sega Genesis / MegaDrive / Master System emulation needs: KegaFusion / Gens.
You will be able to play all your Sega Genesis / MegaDrive / Master System console games with these excellent emulators. KegaFusion is not open source but it is freely available and has some cool features.

For all your video editing tasks: Kdenlive.
A great video editor for Linux/Unix systems.

For all your computing purposes: GNU Linux based Operating System.
Let's face it, average users don't need Windows to be happy or do their work. Are you sick of defragmenting your Windows disks or decreased system performance over time, bloating and viruses!? On Linux you don't have to worry about all of this and better yet: You don't have to pay hundreds of dollars for it, and basic support is freely available virtually anywhere. And forget about all other limitation and absurd rules Microsoft applies to you.

All the programs cited above are free to use, open source and cross platform unless otherwise stated. Why pay for software you are not sure will stay alive forever!? If open source development is stopped it can be resumed by ANYONE.

Did you know? About 100% of average users can be more than happy without Windows or proprietary software.

The main problem with proprietary / closed source softwares (e.g. Microsoft Windows, etc...) is that you don't know what's in there, it can have malicious code and back doors for spying you. That's another risk and problem. Open source software is more important than you imagine.

Then please, do not recommend your friends to download a pirated/cracked or any proprietary software (especially closed source) if he/she does not need it. Let's make the software world better!

Great thread, I'd like to add some of my favorite useful programs to the list, which are not well known like FF or VLC are, but are very nifty. Here's my "top three" I couldn't live without anymore:#1:Always Mouse Wheel - Captures the window you're hovering on with your mouse so you can use its wheel without having to click on that window first. Also prevents unwanted changes to windows you have left. For those of us using multiple screens, it is a very useful tool to have. No install - just adds some registry entries. This must be my favorite program!#2: Ave Folder BG - If you're tired of those blazing white Windows folder backgrounds, this small utility will let you choose any picture you like (of solid color or perhaps a nice pattern?) to replace that eyesore. You can choose the text color as well and it can be applied to sub folders automatically. No install - just run it (adds some reg entries) and let it start with Windows.#3: Registrar Registry Manager - Finally an easy way to search for and delete multiple registry entries, i.e. entries left behind by malicious/unwanted/accidentally installed software that can't be killed by simply uninstalling it. I found it to be very effective and safe to use. It seems to have little restriction on what can be deleted however, so use with caution and only search for exact software names. Advanced users only! Still, this program was the only one that was able to remove the 700+ entries of Kaspersky left over after using their "uninstaller" safely for me, after changing to another AV solution.
So, there's my favorites. There are more, but I'm most happy to have found those three.

See they have so much good stuff but it's impossible to know of it. Like sysinternals and Mouse without borders. Someone there made an awesome program called Canned Response Manager (file name canman.exe) way back and I've yet to come across it (or anything as simple) except at Microsoft related workplaces (when I was there I didn't think of copying it either ). It rested in the systray and stored text. You clicked the icon and you got a list of the text snippets in question. I was seriously thinking about picking up programming just to make it, that was how useful it was.

It's a small basic IP scanner. Ran it on the office machine, discovered I had the entire area avaliable to me. Grabbed a router and plugged it into the local switch (the room is open). The net owners are a bunch of fools, I dislike them immensely.